Manchester United moved level on points with fifth-placed Tottenham after victory at West Ham, who played for 75 minutes with 10 men following the controversial dismissal of Sofiane Feghouli.
Referee Mike Dean showed Feghouli a straight red card after the midfielder's 15th-minute challenge on Phil Jones.
Replays showed it was more of a coming together between two players committed to winning the ball than a reckless challenge meant to cause harm.
Antonio Valencia was guilty of an astonishing miss for the visitors before substitute Juan Mata scored from 10 yards after Marcus Rashford's clever pass.
Zlatan Ibrahimovic was one of three players offside when he doubled the lead after Pedro Obiang's clearance fell to Ander Herrera.